Introduced in the late 1990s, digital television (DTV) technology appealed to the television broadcasting business and consumer electronics industries as offering new consumer services and business opportunities that were impractical with previous analog television. Digital television is more flexible and efficient than analog television. When properly used by broadcasters, digital television allows higher-quality images and sound and more programming choices than analog does. In DTV moving images and sound are sent and received by means of discrete (digital) signals, in contrast to the analog signals used by analog television. Digital television includes, but is not limited to Digital Terrestrial Television (DTTV or DTT), which is an implementation of digital technology to provide a greater number of channels and/or better quality of picture and sound using aerial broadcasts to a conventional antenna (or aerial) as opposed to a satellite dish or cable connection.
The development of digital television has lead to many changes in television broadcasting and related industries. Many countries have mandated a change from an analog television signal format to a new digital format. One example of such a digital television broadcast standard was developed by the Advanced Television Systems Committee. With a conventional analog television broadcast, a video signal modulates a carrier wave signal that is broadcast by a transmission tower. A television set contains a receiver that detects broadcast signals. The receiver includes a tuner that selects a particular channel according to its carrier frequency and a demodulator that extracts the video signal from the modulated carrier signal. With a digital television signal, the video signal is generated in a digital format or an analog video signal is converted to a digital format to produce a digital signal. The carrier wave is modulated according to the digital signal format, e.g., using vestigial sideband (VSB) modulation. This new format allows data for additional digital services to be broadcast along with a regular television signal. Examples of such services may include real time stock quotes, sports, weather and traffic updates and other services traditionally associated with delivery via two-way media, such as the internet, digital wireless services or cellular telephone services.
The delivery of digital services by a primarily one-way medium through digital broadcast presents certain challenges and problems. Conventionally, a broadcast, digital or otherwise sends information on a schedule determined by the broadcaster. Digital services delivered by two-way media, by contrast, may be obtained more or less on demand. Updating information delivered by digital broadcast over multiple broadcast channels presents certain problems heretofore unrecognized in the art.
It is within this context that embodiments of the present invention arise.